I understood your point, but we both also understand that the "who designed the designer" questions are supposed to build up a logical chain to the "inevitable" conclusion that "there is no God."
However, the question is actually irrelevant to the question of life on Earth -- which is the only evidence we have of life in the universe, however it came to be. The unspoken assumption seems to be that there is no other possible type of life: which seems a rather presumptuous claim.
Looking at life on Earth, the bottom line is this: there's no reason for us to rule out the possibility that intelligent designers played at least some role (not necessarily an exclusive, or even a predominant role) on the way life has turned out here. The best reason for not tossing out that possibility is that we humans have been doing intelligent design for millenia.
The real issue here is not science per se, but rather the problem of underlying assumptions. The whole Evolution/Creation/ID debate hinges on certain assumptions about The Way Things Are, and at that level the discussion is almost never "scientific."
I agree with you that there might have been intervention by an intelligent designer. I have always maintained that evolution is in no way incompatible with creationism or ID. (Just with certain interpretations of the Bible) Science has no way of showing that there has been (indeed nor that there has not been) any such intervention, however. This is outside the realm of science and should not be taught as science. If schools want to teach ideas such as this in a comparitive religion or some other appropriate setting, I have no problem with that.